1. Field Of The Invention
The present invention relates to the neutralized addition products of selected unsaturated dicarboxylic acids and selected poly(oxyalkylated) alcohols and their use as anionic surfactants suitable for use in caustic solutions.
2. Brief Description Of The Prior Art
Caustic-soluble surfactants are used today in a wide variety of industries. They are employed in the metal cleaning business to remove greases and process fluids from metal finishes. They are also used in the textile field to remove knitting oils and the like from textiles. They are used in emulsion polymerization reactions to aid the dispersion of one or more of the reactants in each other or in a solvent. They are also employed in dairy/food plants and in bottle washing operations, as well as household and other consumer cleaners.
Commonly used caustic-soluble surfactants include anionic alkylated diphenyl oxide disulfonate-type surfactants (e.g. DOWFAX 2A1 made by Dow Chemical Co. of Midland, Mich.); nonionic alkylated glucoside-type surfactants (e.g. TRITON BG-10 made by Rohm & Haas of Philadelphia, Pa.); and carboxylic acid-type surfactants (e.g. TRITON DF-20 also made by Rohm & Haas). While these commercially available surfactants may be suitable for certain applications, they have certain deficiencies which prevent their use in many applications. Ideally, an excellent caustic-soluble surfactant should have very good surface activity and high caustic solubility (e.g. soluble in aqueous solutions containing more than about 10% by weight NaOH) as well as low foaming properties and a relatively low cost.
Separately, reactions of carboxylic acids with polyols in the presence of a free radical initiator are known. For instance, U.S. Pat. No. 4,250,077 (von Bonin et al.) teaches mixing olefinically unsaturated carboxylic acids with many types of polyols and then polymerizing the mixture with a free radical former to produce a graft polymer. The preferred carboxylic acid (and the only acid used in the working examples) is acrylic acid, which homopolymerizes with itself. It should be noted that this reference does not teach the exact mechanism by which this "polymerization38 reaction is carried out.
U.S. Pat. No. 4,365,024 (Frentzel) teaches making surfactants suitable for incorporation in polyurethane foams by reacting under free radical polymerization conditions a polyoxyalkylene adduct and unsaturated dibasic esters containing 4 or 5 carbon atoms. The mechanism of this reaction is referred to as grafting, i.e. the reaction product is composed of the polyoxyalkylene adduct backbone to which are attached at intervals "grafts" of the unsaturated diester. See column 4, lines 46-51 of this patent. The patent further states that, "In light of the known inability of unsaturated diesters of the invention to homopolymerize, it is believed that the mechanism of the reaction may involve the addition of single diester units to the polyoxyalkylene backbone". The patent specifically teaches that these surfactants may be used in phenolic resin foams, polyisocyanurate foams and polyurethane foams.
U.S. patent application Ser. Nos. 475,785 (Frentzel) and 475,786 (Frentzel et al.), both filed on Mar. 16, 1983, teach making carboxylic acid-containing mono- and polyether polyol addition products by reacting maleic acid, fumaric acid, itaconic acid, or mixtures thereof with at least one polyhydroxy-containing mono- or polyether compound (e.g. a polyether diol or triol) in the presence of a peroxy free radical initiator. These patent applications also disclose making polyurethane prepolymers and aqueous polyurethane dispersions from these carboxylic acid-containing mono- and polyether polyol addition products.
Until the present invention, no one has proposed making surfactants by the free-radical addition of single carboxylic acid units at intervals onto the backbone of a poly(oxyalkylated) alcohol followed by neutralization of these carboxylic acid groups. It was quite surprising that these carboxylic acid-containing poly(oxyalkylated) alcohols have particularly useful properties as caustic-soluble surfactants. The individual single neutralized acid sites on the backbone provide adequate sites for providing caustic solubility, yet are short enough so as not to interfere with the surface activity and low-foaming properties of surfactant compositions as a whole.